Water Balance Modeling of Earthen Final Covers

Abstract

Hydrologic data measured from two earthen final cover test sections constructed on actual landfill final covers are presented with predictions made using two water balance models (HELP and UNSAT-H). Both test sections were constructed as traditional resistive barriers comprised of a compacted fine-grained layer overlain by a vegetated surface layer. Hydrologic and meteorological data including precipitation, air temperature, solar radiation, relative humidity, wind speed, and wind direction were collected at each test section for three years. Percolation, overland flow, and soil water content were monitored continuously. Predictions of the water balance were made using the water balance models HELP and UNSAT-H. In general, HELP overpredicted percolation, sometimes significantly, and UNSAT-H slightly underpredicted percolation. However, both models captured the seasonal variations in overland flow, evapotranspiration, soil water storage, and percolation. UNSAT-H captured these variations more accurately than HELP.